Question

Name two elements each one of which has one electron in its outermost shell.

Answer 1

Step-1: Introduction

The elements in periodic table are placed in periods and groups. Periods are horizontal rows that has increasing atomic numbers. Groups are vertical columns. There are 7 periods and 18 groups in periodic table.

The outermost shell is the valence shell of the element. The elements in groups have similar electronic configuration of the valence shell.

Step-2: To find the valence electrons

Number of valence electrons in the outermost shell = 1

Number of valence electrons = Number of groups

Since the valence electron is 1, the elements belongs to group 1

Step-3: Group 1 elements

The group 1 has seven elements. This group is also called as alkali metals because they form basic hydroxides that are soluble in water.

The two elements that has one electron in its outermost shell are Lithium ($\mathrm{Li}$) and Sodium ($\mathrm{Na}$).

Lithium has 2 electrons in K-shell and 1 electron in L-shell with atomic number 3. Sodium has 2 electrons in K-shell, 8 electrons in L-shell and 1 electron in M-shell with atomic number 11.

Step-4: Final answer

Therefore, two elements that has one electron in its outermost shell are Lithium and Sodium.